Please visit our Sponsors
FAQs on Freshwater Worm (Flukes, Roundworms...) Parasitic Diseases 2

Related Articles: Nematodes, Flatworms, Anchor Worms and Other Worm Parasites of Freshwater Fish by Neale Monks, Freshwater DiseasesFW Disease Troubleshooting, Ich/White Spot Disease, Choose Your Weapon: Freshwater Fish Disease Treatment Options by Neale Monks, Invertebrates for Freshwater Aquariums by Neale Monks,

Related FAQs: Worm Parasites 1, Freshwater Worms, (Freshwater Worms of All Kinds): & FAQs on: FW Worm Disease Diagnosis/Identification, FW Worm Disease Treatments, & FAQs on Parasitic Worms by Group: Platyhelminths/Flatworms: ( Flukes, Planaria, Tapeworms and Leeches), Acanthocephalans, Nematodes/Roundworms (e.g. Camallanus),... Anchor "Worms": See FW Crustacean Parasitic Disease, & Aquarium MaintenanceFreshwater MedicationsFreshwater Infectious Disease, Freshwater Fish ParasitesAfrican Cichlid Disease 1, Cichlid DiseaseIch/White Spot Disease,


Need help with a fish problem    4/23/20
Hi there,
I’ve got a problem with one of my wagtail platy’s. Well, I say problem, it’s dead and I’m not that up to speed with bringing things back from the dead.
i woke up on Monday morning too see it was dead, but there was this huge parasite looking thing coming out of it. I’ve called 5 different places and they don’t really have an answers. Made an account on Fishlore.com to see if they have any answers. They had none. But someone said I should email you and see if you have any answers I’ve attached a picture to help.
I've been keeping fish all my life and I’ve never had this before.. all parameters are fine and well within range.
it’s belly was bulging so I thought it was pregnant, I’ve had lots of fry in this tank.
This thing wasn’t coming out of its gills or through its butt, it was come out the side of the fish just behind the gills. It’s the black dot on side of the fish just behind the gills.
I hope one of you lot can help me diagnose/identify what on Earth actually happened, because I’m seriously stuck here. PS, I apologise for the fact the picture was taken on an Easter egg box.. it was the first thing I had on hand. Didn’t particularly want to handle it too much because a lot of parasites can jump species
Cheers for reading, I hope you can help
<Evidently some sort of 'worm'. The problem is that it's hard to say whether we're talking about an external parasite (which may not in fact be a true worm, but a crustacean of some sort) or was this a worm inside the fish that somehow got out through the wound. Very difficult to be sure without actually having the fish in front of me, together with a decent dissecting lens. In any event: certainly a good idea to treat your fish with Praziquantel (such as PraziPro) or some other reliable anthelmintic. Internal worms are quite common in livebearers, though rarely anything like this. It's worth repeating the course after finishing the first course because worms are difficult to shift. External parasites, particularly crustaceans, are rare in aquaria and difficult to treat. Mostly, they can't complete their life-cycle in aquaria, but some, notably Lernaea ("Anchor Worm") can. Anchor Worms are distinctive because they have a dark, often fork-shaped attachment head that digs into the flesh, as well as a semi-transparent worm-like body that is visible outside the fish, often with two egg-containing structures dangling even further. My gut feeling is that we're dealing with something along those lines; if not actually Lernaea, then some sort of crustacean external parasite. Cheers, Neale.>

Re: Need help with a fish problem    4/23/20
Hi there
That’s absolutely fantastic! Thank you so much for your help, I’ll start the treatment right away!
<Glad to be offer some tentative help at least.>
Goodness you guys are good.
<That's very kind. But do check your photos against pictures of Anchor Worms and suchlike, and see if it is a plausible explanation.>
Well you’re definitely better than the 7 fish shops I’ve emailed and the 4 different forums I’ve posted on.
Can’t thank you enough for that!
Thanks again!
<Most welcome. Cheers, Neale.>

Re: The (Pen)Ultimate Thread---Stocking 105 Gallon Semi-Aggressive Community: NOT: FW worm concern       8/16/15
I have been feeding the blue Acara two kinds of medicated food: a frozen one for marine fish with Praziquantel, and the other with IH-lmidazole (it is New Life Spectrum Hex Shield pellets). I also have fed them Hikari seaweed pellets.
<Sounds good.>
They like the frozen food, but the NLS Hex Shield they find unpalatable.
While they have gained weight, now they have something white protruding from their vents. I suspect it might be an anal prolapse, (I normally feed my fish algae-based food, but neither of the medicated foods are this, so I suspect they are constipated.) If it is a worm of some sort, how would I tell?
<Camallanus worms tend to wriggle and if you tank a photo and look close up, you may even see worm-like features. I agree with you, that the combination of parasites and the medications might be irritating the anus causing it to stick out. Should recover if all's well.>
Also is it safe to use Epsom salts with Zeolite?
<Yes. Cheers, Neale.>

Re: The (Pen)Ultimate Thread---Stocking 105 Gallon Semi-Aggressive Community         8/12/15
Do you have any recommendations for deworming medicines for the blue Acara? I have heard some types can kill small fish, and these guys are pretty small now.
<Read here: http://wetwebmedia.com/FWSubWebIndex/AnthelminthicsFWF.htm
and the linked files above. Search ahead of writing us. Bob Fenner>

cardinal tetras with clear blisters and tiny white worms     6/8/13
Hi Crew,
I have a planted 13 gallon tank....well established for 2 yrs.  2 of my 7 cardinal tetras have developed clear bubble like blisters (mostly near their pectoral fins and mouths). On close inspection there appear to be tiny white worms within or just adjacent to these blisters.  My other species (Ram, Corys, platy) are unaffected.
<Mmm, could be... Nematodes, other>
Others have posted about this problem on other websites but there are no definitive opinions on diagnosis or treatment.  I am suspecting they are tiny roundworms.  It is interesting that this seems somewhat unique to cardinals.
<Yes; possibly>
Any suggestions would be appreciated. If I can get a good picture I will send it.
<If you can, please do>
kind regards,
<I would try introducing an anthelminthic via foods... lacing ahead of offering. Okay for all to consume. Likely Praziquantel would be my/your first compound to trial. Bob Fenner>

Free Living Nematodes Dangerous to Humans?  6/26/12
Hi There.  I am working on eradicating a free living white nematode population in my freshwater snail tank.  My questions is: Are they dangerous to humans?  I'm usually quite careful to wear gloves when I clean the tank, but today some tank water (with nematodes in it) splashed on my leg.  I shave my legs, so I might have some microscopic cuts. 
Any advice would be greatly appreciated!
<I very much doubt there is, or will be an issue here. Human parasitic Roundworm issues are principally a matter of ingestion (eating, drinking)... the few burrowing types (e.g. swimmer's itch) involve being in infested water for extended time... I would not worry. Bob Fenner>
Re: Free Living Nematodes Dangerous to Humans?  6/26/12

Thanks Bob.  I appreciate your quick response!
<Ahh... we don't post our "classes attended" to our bio.s on WWM, but I had two semesters of Parasitology and some related med. classes (e.g. histology), and have had an earnest interest in such matters in the intervening decades. IF you are truly concerned, I would consult w/ a (likely tropical) medicine specialist. Cheers, BobF>

Re: Black moor with digestive troubles-- 03/20/11
Hi Neale:
Well, it has been several weeks now and my poor little moor is hanging in there but is still not well.
<Oh dear.>
Its colour has faded and it has ongoing motility problems. It swims normally for a few seconds, then swims backwards in a strange "hiccoughing" motion. It is still extremely constipated, presenting with long, trailing feces, some of which is so fine it looks like a single strand of cobweb.
<Mucous perhaps? Or a single fine worm, e.g., a nematomorph?>
Metronidazole-based food did not work, nor did Praziquantel-based food, peas or abstaining from treatment. Not surprisingly, it is beginning to have flotation issues.
I have located a de-worming flake food that contains Fenbendazole at an online store called Angelsplus.com. You suspected this fish was infected with helminths and I think that it might be prudent to try to treat for this now before I lose this little fish. I wanted to pass on the name of the webstore (as long as it doesn't violate some rule of your website) because it is the only place that I found that carried a Fenbendazole-based food: hopefully this information might help someone else who is having similar tank troubles. The company is based in the US but they do ship to Canada (I'm not certain about the UK).
<Thanks for sharing this information.>
I have not been able to use a microscope at work so if this fails my next step will be to have the fishes feces tested for parasites. This is an expensive option that I am hoping to avoid. I will let you know if this food works for the moor or not.
<I'm actually very impressed by your care here; most fishkeepers would have called it a day with this Moor, and either euthanised it or simply ignored its problems.>
Kind regards:
<Good luck, Neale.>
Re: Black moor with digestive troubles   3/20/11

Hi Neale:
I Googled "nematomorph" and discovered a whole new world of things I'd rather have not viewed before breakfast! It could indeed be a single worm- I have no way of telling without a closer look.
<Indeed, that is the case.>
It is so difficult to decide what to do or which medication might be effective. <<None. RMF>> I don't want to kill the fish by using too many medications. The fish also has a tank mate (who is asymptomatic except that it has not grown since I purchased it as a near-fry several months ago). The failure of this second fish to grow does seem to indicate some sort of worm.
<Would seem likely.>
Do you think that a Fenbendazole food is the next most logical step? What should I do about potential eggs or larva in the tank? I have increased my water changes/vacuuming for this one tank to three to four times per week since the fish has become ill- is this helpful? The water changes are quite small as I don't want to disturb the biological filtration. I have also been changing the carbon in the filter once a week.
<If you're treating for worms, yes, it makes sense to treat the whole tank.
Antihelminthic medications shouldn't affect biological filtration, but do keep an ammonia or nitrite test kit to hand just in case the fish start behaving oddly.>
I can't bear to euthanise since the fish are both still active and interested in food. If this changes I will have to consider this option but I am hoping I will be able to report otherwise.
<Good luck, Neale.>
re: Black moor with digestive troubles   3/20/11

Thank you! I have done some more "Googling" and found two very good articles regarding antihelmith medications. The first is a research paper comparing six antihelminthic drugs:
So I am wondering if Levamisole HCl might be a better alternative than the Fenbendazole food since I need to treat the entire tank. Which led me to the second article in a loach
forum: http://www.loaches.com/disease-treatment/levamisole-hydrochloride-1 
However, I can't seem to find a supplier for Levamisole HCl in Canada (since it is a cattle dewormer I find this odd- perhaps it goes by a different name). I may be able to purchase from the US if it is not a
restricted item.
<Only Praziquantel and Flubendazole are sold over the counter in the UK, and this may well be the same in the US.>
In your experience, what is the most effective treatment?
<No experience at all here! Never had to treat for worms. For whatever reason, worm-infected fish do not seem that common in the UK retail side of the hobby. I'm sure worm-infected fish do get sold here, but compared to other sources of mortality, they just don't seem to be significant outside very specific niches such as Discus. With that said, products like Sera Tremazol, Solupraz and Wormer Plus are sold/used here, and seemingly successfully.>
Many Thanks:
<Cheers, Neale.>
Re: Black moor with digestive troubles  3/22/11

Hi Neale:
I did find a supplier of Levamisole in the US so if the parcel doesn't get stopped at the border I should have it in a couple of weeks. It seems a long time for my poor fish to wait but it has been a real trouper through all of this. I can only hope I am targeting the right parasite/worm. I've ruled out Trematodes and Hexamita so I'm keeping my fingers crossed..
<Me too!>
In the meantime I am saving up for a decent microscope!
I will let you know what happens with the little moor.
<Thank you, and good luck! Cheers, Neale.>
re: Black moor with digestive troubles, Flukes  4/7/2011

Sorry to bother you again, Neale (and WetWeb team):
Well, I have found flukes in all of my tanks- the highest populations are in the tanks without UV sterilizers though even these have a few rogue critters. As I mentioned, I cannot identify the exact species but can say for certain that they are viviparous and I would like to try to eliminate them!
<Indeed.><<and, very common w/ goldfish in most places in the world. RMF>>
I understand this is quite difficult and involves prolonged treatment.
<Can do. Otherwise, best to remove your fish, bleach what you can, discard the rest, and then cycle a whole new filter.>
Is there a safe and effective way to rid my tank of these pests?
<Are we talking about Flatworms (free-living Platyhelminthes) or true Flukes (parasitic Platyhelminthes, Trematoda and Monogenea, on the skin and/or internal organs of your fish, e.g., Dactylogyrus)? Free-living Flatworms are extremely common in aquaria and pose no particular risk, though large numbers of them suggest less than pristine conditions in the tank. No treatment is needed. For things like Dactylogyrus then the usual treatment is an anti-helminthic such as Praziquantel, though a vet may well propose alternative, better medications.>
I would have to treat the tanks so anything that will not kill off the filter media (but will eliminate all the flukes that are hiding in there)
would be best. Has anyone had luck with complete eradication?
<Praziquantel should not exhibit any antibiotic/antibacterial effects.>
<Cheers, Neale.>
Re: Black moor with digestive troubles, Flukes    4/8/11

Hi Neale:
Yes, I am 99.9% sure that these are flukes- they have a widely segmented body and hooks at the distal end that they use to attach themselves to debris in the tank while they twist around looking for food.
<So they are free-living? Not all flatworms are parasites.>
When they detach they move with an extension-retraction motion (sort of like a caterpillar).
<The Monogenea have suckers and hooks around the mouth; Digeneans typically have two "mouths", one the mouth itself, the other a kind of sucker. In Digeneans, the life cycles are often so complex they cannot be completed under aquarium conditions. I'm sure there are exceptions, but these appear to be rare. Under aquarium conditions -- as opposed to pond conditions -- the more probable "flukes" are Monogeneans, which usually have a single host, i.e., the fish in this instance. Dactylogyrus is probably the most common. There are numerous treatments used on fish farms, some of which may be applicable to aquaria, notably Praziquantel; do see a good fish health book for details and arguments in favour of one treatment over another.>
I can clearly see a developing fluke within the fluke. I have not found them on my fish but will do more systematic sampling to be sure. I have not taken gill sample for fear of damaging the fish (is there an easy way to take a gill sample or swab?)
<Not on small, ornamental fish species.>
As I mentioned, I have not been able to identify this fluke from resources on the internet. These creatures do seem to inhabit the buildup in the filter and the annoying spots of brown algae that occasionally bloom in my tank. Is there a species of free-living, harmless fluke?
<All Monogenea and Digenea are parasitic. Free-living flatworms do not have suckers, and typically glide across flat surfaces. Do also be aware of free-living leeches, as opposed to parasitic leeches.>
I really do like the idea of cycling new media and cleaning the tanks. I have just read that Prazi over a period of 21 days may be effective but am loathe to medicate my fish for such a long period of time unless Prazi is indeed safe for such a long-term application.
<About as safe as any medication.>
If I do opt for the first method, what is the best way to ensure that I don't transfer a fluke to the new tank via the fish when I transfer them?
<You can't. By definition, a live fish can carry across parasites, and indeed this is precisely why releasing Goldfish and other ornamental fish into the wild is such a risk -- any such fish could carry parasites from fish farms and/or the tropics into the wild. Treating in a hospital tank with a Zeolite (non-biological) filter may help break the cycle.>
Thank you:
<Cheers, Neale.>
re: Black moor with digestive troubles    4/8/11

Thanks again, Neale:
I will try to find a good book so that I can identify this fluke. It most resembles the Gyrodactylus fluke but the distal end is different (it does not have the polydactylous hooks). It also has a very characteristic single
stalk that looks like the eyestalk of a snail or slug near the head. I can't find this anywhere (ah, maybe I have discovered a new fluke! The Monogenea Almedius..). At any rate, I will take some more samples from my fish to see if I can find any on the actual body surface. If I find out what this is (or if I can afford a camera attachment for my microscope) I will send along the info!
What frustrates me the most is that this is my fault.. though I have been very careful to quarantine new fish (I usually do so for two months) I became complacent and began using the same vacuum on all of the tanks near the end of my last quarantine. Sigh.
<Hello Gina. Thanks for the update, and I commiserate with the feeling that you, the owner, have somehow created the problem you're having to deal with. We've all been there. Life doesn't have an Undo button unfortunately, so you have to live and learn. Good luck, Neale.>
re: Black moor with digestive troubles. More worm spec., now Rotifera, Nematoda   4/10/11

<Hello Gina,>
I have never been so happy to admit I was wrong! I have finally found my creature- and it is NOT a fluke. It is, in fact, a rotifer. I can't find the exact species but it is one of the Bdelloid rotifers and looks very much like the Philodina gregaria (and is possibly a sub-species).
I had identified other rotifers in the water (beautiful stentors and other unidentified, round, fat rotifers) but I missed the cilia on these ones as they move too much to be able to focus the scope. I found one this morning that had the decency to die without contracting and was able to zoom in it a bit better. This explains why I find the greatest concentrations in the filter and why the "foot" does not have the hooks typical of a fluke. They do look very fluke-like and move in the same fashion so I can see why I got confused.
<I can understand the confusion, and I'm very pleased to hear the good news. I will make the observation that excessively high concentrations of any microbe, good or bad, could suggest issues with aquarium cleanliness, so keep an open mind there.>
This just leaves me with nematodes to deal with in two tanks. I am sure that won't be fun, either but at least I don't have to worry about flukes at the same time!
<Indeed. Free-living nematodes aren't a problem, but Camallanus worms are perhaps the most annoying of the parasitic forms found in aquaria. Not too difficult to treat, but do bear in mind that carbon and excessive amounts of organic material in the aquarium (silt, mulm, etc) can reduce the efficacy of any medication. Cheers, Neale.>
re: Black moor with digestive troubles... Nematodes, free-living   4/11/11

Thanks Neale:
Ah, yes, I do think the nematodes I have found are of the free-living sort as they are found in scrapings from the inside of my filter. They most closely resemble "vinegar eels" though I have not found them swimming in samples of tank water, only in filter detritus.
<I see. Harmless.>
I have taken dozens of samples of fish waste and have not found any worms with the exception of one sample I gathered from the bottom of the tank that I suspect had been sitting there for a few hours and had been infiltrated by the worms. The rest of the samples have been more recent.
This is both good and bad as this means that I have failed to identify the trouble with my poor little moor (which is still alive but not very perky).
<May simply be poor genes or some other syndrome we can't identify or treat. Just as humans have hundreds of different diseases, so too do fish, and as hobbyists we are only familiar with a few of them.>
I did find one evil-looking nematode with a stylus but this was in my Oranda tank and I have not been able to find another. Samples of my Oranda's waste has some sort of very small worm (?) or other fast-moving
creature that I cannot identify as it is very hard to see even at 1600x. This may be normal- I can't find any information on the web about what normal fish poop should look like under a microscope!
I do very regular maintenance on my tanks- I do small water changes/vacuuming a minimum of twice a week and I change the filter pads or squeeze out the sponges every 4 to 6 weeks. Perhaps this is not enough- should I adjust my filter maintenance, perhaps?
<This does all sound adequate.>
My fish are fed home made gel food which is made of a large variety of blended vegetables and Spirulina algae- I don't put it into the tank directly, I have, ah, trained my fish to take bits of food off of a small
spoon. I didn't think there was excess food left in the tank but perhaps small bits are escaping. This would be great fodder for nematodes and rotifers I should think.
<Likely so, but in itself, not a problem. Most, likely all, tanks have some sort of microbial fauna, and this plays a key role in the biological filtration process. Without them, the solid wastes from your fish wouldn't
get broken down into the particles and dissolved chemicals your filter can handle.>
Anyways- thank you so much for your help, Neale. It has been quite a journey trying to save the black moor: I guess part of trying to find the source of a problem is to rule out what isn't a factor!
<Glad to help and listen. Cheers, Neale.>

Help with a worm issue please   8/22/09
My Husband went home today and found our Goldfish dead. There was a worm that was working it's way out from inside of the gill. It was as wide as a pencil eraser, It was white with reddish orange, maybe an inch long but it was coming out of the gill and then going back into the fish through his side. VERY nasty!!! What is this? I have 3 other fish in the tank. A catfish and 2 black goldfish. Do you think they are infected???
<Possibly. You will need to use a proprietary anti-helminth medication since there's a chance the other fish are carrying worms as well.
Medications that contain Levamisole, Piperazine and Praziquantel are often recommended, but they don't work reliably, so if you can, use medications with Fenbendazole or Flubendazole instead. Do also be aware that some crustacean parasites, such as Anchor Worms and Gill Lice can look worm-like at first glance, and nothing you have said here helps me identify the problem either way, so you should use a search engine of your choice to find photos of these, and then act accordingly, since different medications will be required. Do be aware that some medications can be toxic to catfish, and do also remember that parasites often become problematic only when the fish are stressed, so review environmental conditions. Three Goldfish would need 40 gallons or more, and big catfish, such as "Plecs" (usually Pterygoplichthys species) can't be kept safely in tanks less than 55 gallons in size. So if you have a small tank, less than 55 gallons, poor
environmental conditions could easily be part of the problem. Cheers, Neale.>

Worms, Constipation or Dropsy?  6/9/09
My 13 year old son has a Columbian Tetra
<Is a very social species... not well kept singly... needs to be in a group... but in a larger system as well than I read you have below>
with some problems. We are fairly certain he is a male. A few days ago we noticed it looked as if he swallowed a marble as he bloated up very quickly. He is acting almost normal - a little lethargic, tends to swim away when approached, breathing a little more heavily. He was on a diet (almost entirely) of flake food.
<Ahh! Likely at least a good part of the issue>
I suggested feeding some shelled, green pea,
<Look to Brine Shrimp, Daphnia...>
thinking he might be constipated. He did eat a little. He has continued this way, neither growing slimmer or fatter for 5 days now. We have halted the flake food, and are only offering pea, which he does not have too much interest in.
<Would you be? Not I>
He does not appear to be pineconing, but yesterday I noticed he had a bright red "tread" coming from his anal area. It is quite long and stringy - with no stiffness to it (i.e.: free flowing - like a polyester thread as opposed to a hair). At first I thought it was a constipated poop, but it hasn't changed (dropped off) in a day. He's in a 10 gal tank with another Columbian Tetra, 2 harlequin Rasboras and a shrimp. Everyone else appears o.k. I hope my descriptions help as I'm not entirely sure we're dealing with worms here. Any thoughts or ideas?
Thanks very much,
Glenna Hauck
<Again, the crustacean food/s (frozen/defrosted is fine) are your best route here to mix in regularly... as laxative. Bob Fenner>

Become a Sponsor Features:
Daily FAQs FW Daily FAQs SW Pix of the Day FW Pix of the Day New On WWM
Helpful Links Hobbyist Forum Calendars Admin Index Cover Images
Featured Sponsors: